We are interested in VECSEL architectures dedicated to CPT (Coherent Population Trapping) atomic clock experiments. The active structures are designed to emit on one of the transitions of the cesium atom (Cs) at 852 nm or 894 nm. The laser emission consists in two perpendicularly polarized laser lines, at two frequencies distant from 9.2 GHz corresponding to the hyperfine clock transition .
In this architecture, the frequency difference between the two laser lines is tunable, and the beat signal has a high spectral purity. We have demonstrated that it is possible to control the absolute frequency of the laser and the difference between the two frequencies. With this laser source, we have obtained a first CPT spectroscopy signal . We have particularly studied the different contributions to the laser noises (intensity, frequency, phase) and predicted that the intensity noise of the pump source would limit the short-term frequency stability of the atomic clock in the studied configuration [2,3].